An IMEDEA (CSIC-UIB) study based on the use of genetic and oceanographic data maps the commercial fish larval dispersal

Researchers at the Spanish National Research Council at the Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB), at the Center for Advanced Studies of Blanes (CEAB), at the University of Barcelona, and at the University of Salento (Italy) have published in the journal Molecular Ecology a scientific study that determines the gene flow between populations of Serranus cabrilla and how larval dispersal is closely linked to currents through barriers or oceanographic fronts in the Mediterranean.One of the authors of the study, researcher Celia Schunter, at the CEAB, states: “we have observed that larvae from Alboran Sea always go to the coasts of Murcia and Alicante, in Spain, and never the reverse, and the larvae from Alicante go to the Balearic Islands and not towards the coast of Castellón. Also, the larvae of Castellón can go to Alicante, but not the other way. The Balearic Islands do not export larvae, so that their populations are only maintained by the larvae produced by adults that inhabit the islands and small imports of larvae from the Alicante area”.

This means that in a situation of over-exploited stocks in the region of Murcia and Alicante, which import larvae from the coasts at its north and south, populations will recover more easily than those of the Balearic Islands, which basically just draw on their own populations. Furthermore, the combination of genetic and oceanographic data has allowed to verify that the seasonal changes in currents and spawning season may also have an important role in the structure of populations, in the case of Serranus cabrilla and also in other species of great commercial value, such as grouper (Epinephelus marginatus).

To elaborate the study more than 300 Serranus cabrilla were sampled from 13 locations in the Mediterranean, and oceanographic data were taken throughout the Spanish Mediterranean coast. Four genetically distinct groups were identified, with a clear division located on the discontinuities in the oceanographic channel of Ibiza, the Almería-Orán front, and the Balearic front.

Thus, the study evaluates the connectivity model of Serranus cabrilla with genetic markers, and identifies the various genetic units of the species, as well as the direction of gene flow. The researcher at the IMEDEA (CSIC-UIB) Joaquim Tintoré, also author of the study, said: “With the help of satellite oceanographic data and dispersion model simulations, we analyze the flow of particles to evaluate the influence of the model of predominant currents on the genetic structure of Serranus cabrilla”.

Advances on fishery management and marine reserves

Recent studies indicate the enormous influence of oceanographic processes and dispersion models on the connectivity of fish populations. “Seventy percent of all marine life has a pelagic larval phase in their life cycle, but the difficulties in studying the early stages of its life still limit understanding of how connectivity works in the marine environment. This study shows that it is essential to consider oceanographic data in population genetics studies, not only to understand the connectivity, but also to study the directional patterns of dispersion. This can have a major role in fisheries research and the establishment of marine reserves, as it determines how different exploited populations are connected and how to optimize the conservation of species”, concludes Henry MacPherson, biologist at the CEAB and author of the study.